Optical and magneto-optical disks are capable of storing data very densely. A five inch diameter optical disk, can store approximately 1.2 gigabytes of data (one gigabyte per side). Accordingly, it is common to use optical and magneto-optical disks as storage devices for large collections of files, such as databases, image files and video files.
Devices which are commonly termed "jukeboxes" are available for use in optical disk database applications in which large amounts of data are stored on a plurality of optical disks. A jukebox includes a disk reproducing or recording/reproducing apparatus and a storage rack having a plurality of storage slots for storing a plurality of optical disks. Robotics are provided which are capable of removing a disk from any particular storage slot, transporting it to the reproducing apparatus, and inserting it into the reproducing apparatus. Thus, data on any one of the plurality of disks contained in the storage slots of the jukebox can be reproduced. In such a system, the jukebox would be coupled to a local computer which receives requests for data from a user at the computer or from remote clients over a network. The computer has a hard disk drive in which is stored a jukebox file system which is basically an index into the database stored on the jukebox. The application software, using the jukebox file system, processes the requests and identifies the file name and disk containing the requested information and generates commands to control the robotics and reproducing apparatus in the jukebox to retrieve the specified file.
A standardized protocol known as SCSI (Small Computer System Interface) is the most common protocol used in small computer interfacing systems. Accordingly, most peripheral devices, including jukeboxes, operate in accordance with SCSI protocol. Accordingly, the jukebox would be coupled to the workstation through a SCSI cable and the workstation would send SCSI format commands to the jukebox for controlling the jukebox's robotics and data reading operations to retrieve the requested data. The jukebox would send the data back to the computer for forwarding to the user/client.
A typical jukebox may have storage slots to accommodate 20 disks. Accordingly, such a jukebox would be able to provide access to approximately 26 gigabytes of information. If it is desired to have access to more than 26 gigabytes of information, there are several options.
First, one can purchase a jukebox with more slots. However, jukeboxes with capacity greater than 20 disks are expensive. As a jukebox user's capacity needs increase, he may replace his existing jukebox with a larger one, but he will lose his investment in the initial jukebox. Further, if and when the user outgrows any subsequently purchased jukeboxes, he will have to continuously replace the previous jukebox with increasingly more expensive jukeboxes with no use for the replaced jukebox.
Alternately, one can couple an additional jukebox to the workstation through a second SCSI interface. However, there are a limited number of SCSI peripherals which can be supported on the SCSI protocol. In particular, in the SCSI protocol, only 8 addressable peripherals are supported per SCSI interface module. Each jukebox requires three of those addresses, namely, one address for the robotics, and two addresses for data transfer operations. An additional address is needed for a SCSI controller. That leaves three addresses available. Accordingly, at best, one additional jukebox can be added. If the workstation has another peripheral device, such as a hard disk, then there is not even room for one more jukebox. One can add additional SCSI interface modules in order to support more jukeboxes. However, in addition to the above-noted problems, SCSI cables should not exceed 3 meters in length because of possible data loss due to noise on the cables. Even further, a user would not be able to access the data in different jukeboxes conveniently. The user would have to switch between peripherals (e.g., in DOS, he would have to change directories) in order to switch between jukeboxes.
As a further alternative, additional disks can simply be stored off line and, when data is required from those disks, they can be manually inserted into the jukebox.
Each of these options has significant limitations with respect to the amount of total data which can be made available on line within reasonable expense, with speedy data retrieval and without the need for human intervention.
Accordingly, it is an object of the present invention to provide an improved jukebox based data retrieval system.
It is a further object of the present invention to provide a jukebox data retrieval system with virtually limitless data capacity.
It is another object of the present invention to provide a turn-key jukebox which can be easily installed on an existing system when it is necessary to increase data storage capacity.
It is yet a further object of the present invention to provide a jukebox which can be coupled to a network.
It is yet another object of the present invention to provide a jukebox data retrieval system in which additional jukeboxes can be coupled to a network without the need for additional jukebox controllers for each additional jukebox.